[SCSI] ALUA: send STPG if explicit and implicit is supported

alua_activate only sends a STPG if only explicit is suppored.
As a result, for EMC targets that support both we end up doing
a implicit failover when X commands are finally sent to
the other SP.

This patch does a AND on the h->tpgs, so we do a explicit failover
right away.

Signed-off-by: Mike Christie <michaelc@cs.wisc.edu>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>